Boyd, 28, is cruising toward a possible All-Star nod for the first time, as he's 5-4 with a 3.08 ERA, 1.04 WHIP, and 105 strikeouts in 84 2/3 innings. He's also under team control for several more seasons. Boyd isn't eligible for free agency until after the 2022 campaign.

Castellanos is slated to hit free agency following this season and has been the subject of trade rumors dating back several years. The 27-year-old had a career year last season but hasn't experienced the same success so far this campaign. He's hitting .262/.312/.452 with seven home runs in 61 games entering Wednesday.

Greene has one more year of arbitration remaining and should generate interest with his American League-best 19 saves to go along with a 1.04 ERA and 0.81 WHIP in 26 innings.

Detroit is in the midst of a significant rebuild, which was kick-started when they traded Justin Verlander to the Houston Astros in 2017 and continued when they selected projected future ace Casey Mize first overall in the 2018 draft.

The club will be looking to further boost its farm system that currently boasts four top-100 prospects - including Mize - according to MLB Pipeline.